This disclosure relates to martensitic stainless steels and, more particularly, for a method of processing the steel to achieve balanced mechanical properties and to retain corrosion resistance in the final article.
Stainless steels are generally used and known for their resistance to corrosion. Chromium in the composition of the stainless steel is the primary element responsible for the good corrosion resistance. The chromium is also relatively reactive in the composition and combines with carbon during processing to form chromium carbide compounds at both the grain boundaries and in the body of the alloy grains. Martensitic stainless steels that have relatively low carbon content and high chromium content are particularly vulnerable to forming carbides upon carburization. The formation of the chromium carbide compounds, such as during carburization, depletes the bulk steel matrix of chromium. The addition of carbon in the carburization process generally works to produce a hardened case on a stainless steel part, but the formation of the carbides depletes chromium from the bulk matrix and renders the carburized case substantially less corrosion resistant than the core of the part. The carburization of stainless steel thereby negates the corrosion resistance that is often sought in the use of the stainless steel.